Microwave dynatron oscillator



Dec.r26, 1950 E. R. JERvls 2,535,137

MIcRowAvE DYNATRoN oscILLAToR Filed sept. ze. 1949 IN VEN TOR. [PA/57 A? da@ l//S TTE' n ABVM/@ /4 T TOP/Vf Y Patented Dec. 26, 1950 UNITED STATES PATENT OFFICE MICROVAVE DYNATRON QSCILLATOR Application September 28, 1949, Serial No. 118,219

8 Claims. (Cl. 315-39) This invention relates to electron discharge tubes. and more particularly to such tubes for use at very high or microwave frequencies.

A principal object of the invention is to provide an improved oscillator-generator tube of the dynatron type.

Another object is to provide a novel construction of microwave dynatron oscillator.

A feature of the invention relates to a microwave dynatron tube having a central primary electron-emitting cathode and a plurality of focussing and deflecting electrodes symmetrically mounted around the cathode and cooperating with a series of dynodes and output anodes which also symmetrically surround the cathode; the anodes and dynodes being directly formed with `extensions constituting integral cavity resonators.

Another feature relates to a microwave dynatron tube having all the electrodes symmetrically 'disposed around a common central primary electron-emitting cathode, the dynodes and anodes being in the form of spaced metal blocks with the adjacent spaced faces of the blocks acting respectively as dynodes and anodes, and with the `blocks formed with integral cavity resonators which are excited to resonance directly by the Vassociated dynodes and anodes.

A further feature relates to an improved oscillation generator employing dynodes and anodes which are shaped and disposed with relation to each other to eect a more efficient coupling between the secondary electron streams and the output circuits through the intermediary of I cavity resonators which are integrally formed with the dynodes and anodes.

A further feature relates to the novel organization, arrangement and relative location and interconnection of parts which cooperate to provide anI improved microwave dynatron oscillator.

Other features and advantages not particularly enumerated.` will be apparent after a consideration of the following detailed descriptions and the appended claims.

In the drawing,

Fig. 1 is an elevational view of a tube according to the invention.

Fig. 2 is an enlarged sectional View of Fig. l, taken along the line 2-2 thereof.

Fig. 3 is a typical schematic wiring diagram of the tube and its circuit for generating sustained microwave oscillations.

Referring to the drawing, the tube may comprise any suitable evacuated enclosing bulb or lenvelope I, within which is supported the electrode assembly or mount 2. The tube l may be attached to any conventional base 3 which carries the usual plug-in contact prongs 4. The various electrodes of the mount 2 are connected to the respective prongs t in the usual manner. The electrode assembly or mount comprises a central electron-emitting cathode 5 which is preferably of the unipotential indirectly-heated type, such as is well-known in radio tube constructions. Fer example, it may consist of a tubular metal sleeve 6, the exterior surface of which is coated with any of the materials which emit primary electrons when raised to a sufficiently high temperature. Suitably located within the sleeve 6 and insulated therefrom is any wellknown heater wire for raising the cathode to emitting temperature. Disposed symmetrically on opposite sides of the cathode and partially surrounding the same, are two curved metal electrodes 8, e. whose spaced edges form diametrically opposite windows for the passage of the primary electron beams from the cathode. The electrodes 8 and 9, instead of being formed of separate metal members, may for example ne constituted of a single cylindrical metal member having two of its opposite sides provided with Windows for the emergence of the primary electrons. Mounted in alignment with each of these windows, is a pair of diametrically opposite curved plates it, il. These curved plates preferably are formed of cylindrical sectors and are located in outwardly radially spaced relation with respect to the above-mentioned windows. The electrodes 8. 8, l0, I l, are arranged to be connected to ground or to a suitable negative potential. so that each pair of electrodes, for eX- ample electrodes 8 and H, acts as deflector and focussing electrodes for the primary electrons, causing them to follow a curved trajectory and to be focussed into a beam represented by the lines i2. Likewise, the electrodes 9 and ll form the primary electrons into another focussed beam i3. Similarly, the electrodes 9 and El) form the primary electrons into a third focussed beam lil, and the electrodes HJ and 8 form the electrons into a similar fourth focussed beam l5.

Surrounding all of the foregoing electrodes are four metal blocks i6, I1, IB, i9. These blocks may be cut from a single cylindrical metal block having a central bore 20, and with four symmetrically-spaced lateral bores 2|, 22, 23, 24. This single metal block is then provided with four slits 25, 26, 21, 28, each slit being in radial alignment with a respective one of the bores 2|-24. Likewise, the inner wall of each of the Ycollector or anode.

bores 2|24 is provided with a slot or passage 29, 30, 3|, 32 in such a Way that these slots or passages extend substantially tangential to the curved Walls of the respective bores. In effect, therefore, the single block is formed into four separate and similar blocks which are electrically insulated from each other, so far as direct current is concerned, and these four sections of the block are mounted for example on individual supports, not shown, so that the ilat walls 33, 34, 35, 3B, of the blocks il and i9 are located respectively at the regions where the respective primary electron beams i2-I5 are focussed. It will be observed, therefore, that the primary electrons strike these flat Walls 33-36 at somewhat glancing angles of less than 96 degrees. In accordance with one feature of the invention, the walls 33-35 are treated or coated with any suitable material which acts as a copious source of secondary ciectrons when bombarded by the primary electrons. 'Theblocks Il and I9 which carry the vsecondary emission coatings on their flat Walls 33-35, are connected to a suitable positive high voltage direc't current potential, for example positive 40G volts, and the blocks le and i8 are connected to a somewhat higher positive direct current potential, for example G volts. Consequently, .each of the surfaces 33-35 acts as a dynode, and the cooperating spaced i'iat face of the associated anode block acts as a secondary electron In accordance with wellknown theory, when the surfaces 33-35 emit secondary electrons, there exists a negative resistance characteristic in each of the passages 29-32. Each of these negative resistance passages lis in direct communication with the corresponding bore 2l-24. These bores can be designed of such physical dimension and shape, as is Well-known 'in the cavity resonator art, so as `to resonate at a particular frequency for which `the tube is to act as an oscillation generator.

When the tube is in operation, the primary electrons from the four beams I 2-|5 strike the respective secondary emitting surfaces 34, 35, 32 and v'5:43, which release therefrom a copious supply of secondary electrons which travel across the respective passages 3U, 3|, 32, 29, thus imparting 'by well-known dynatron action, a negative resistance characteristic across these passages. By reason of the dimensional configuration of the bores '2l-2l! which causes them to resonate at a particular frequency, this negative resistance characteristic of the respective passages will cause the associated cavity resonator bores to be subjected to charging oscilations at a particular frequency. Each cavity therefore continues to oscillate at its resonant frequency so long as the corresponding primary electron beam strikes its respective secondary emission surface. In accordance with known design formula, each cavity 2 l--24 will have a certain shunt resistance which vis a function of the cavity shape and size, and the spacing between the walls of the associated passages 29-32. Ordinarily, this shunt resistance of a cavity resonator, would have a positive value. However, by setting up a negative resistance characteristic across each of the passages 29-32 as above described, and by having dilferent Vdirect Ycurrent vpotentials applied to the opposite Walls of each passage, the negative resistance overcomes the conventional positive shunt resistance of the associated cavity, thus inducing the vgeneration of sustained ultra-high-frequency oscillations in each cavity. If desired, one of the cavities can `be provided with a lsmall inductive loop 31 or probe which can be connected by Way of a concentric wave transmission line to a suitable load.

Fig. 3 shows schematically one typical circuit connection of the electrodes and the manner of connecting the tube to the output or load circuit. In this figure, the parts which correspond to those of Fig. 2, bear the same designation numerals. However, for purposes of schematic illustration, the several cavities are represented by a single equivalent single-turn inductance 38 and With a single equivalent inherent capacitance 39.

In addition to the advantages of the construction as above pointed out, there is the additional advantage that the slots or passages 2.9-32 can be positioned so that the secondary emission surfaces 33-36 are oriented with respect to the impinging primary electrons so that the said primary electrons strike said secondary emission surfaces at the optimum of less than grazing angle for maximum secondary emission. Furthermore, the blocks lli-i9 being integral with the secondary emission surfaces act as highly efficient heat dissipators thus maintaining the said secondary emission surfaces at the required relatively low temperature.

While one particular embodiment has been described herein, it will be understood that various changes and modications may be made therein without departing from the spirit and scope-of the invention.

What is claimed is:

i. fin electron tube of the dynatron type comprising evacuated enclosing envelope, a central primary electron emitting cathode, means a plurality of cavity resonators symmetrically surrounding said cathode each of said resonators being formed of a pair of spaced adjacent grooved blocks with one set of adjacent edges of each pair of blocks forming a respective passageway extending parallel to the length of said cathode, one wall of each passageway being an emitter of secondary electrons, and electrostatic electron deiiector means located between the cathode blocks to form the primary electrons from the cathode into a series of discrete beams having curved trajectories which terminate at said one wall of a respective passageway.

2. An electron tube of the dynatron type, comprising an enclosing evacuated envelope, a central primary electron emitting cathode, electron deflecting and focussing electrodes surrounding the cathode for forming the primary electrons into a series of electron beams, e, plurality of dynode surfaces surrounding the cathode one for each of said beams and upon which the corresponding beam imninges, an anode surface for each dynode surface and spaced therefrom to form a dynode gap, and means integral with each pair of dynode and anode surfaces dening a cavity resonator local thereto to be excited by the secondary electron emission in said gap.

3. An electron tube of the dynatron type, comprising an enclosing evacuated envelope, 4a central electron emitting cathode, a plurality of metal blocks surrounding said cathode said blocks being mounted in spaced adjacent pairs insulated from each other for direct current and with the adjacent walls forming a cavity resonator, said blocks having a common central well Within which said cathode is mounted, electron deflecting and focussing electrodes located in said well around said cathode for forming the primary electrons into a series of discrete beams, and a 'passageway extending from each cavity resonator to said central well, one wall of each passageway being an emitter of secondary electrons and upon which a corresponding one of said beams may impinge.

4. An electron tube according to claim 3, in which one block of each pair is connected as a -dynode block and the other block of each pair is connected as an anode block.

5. An electron tube of the dynatron type, particularly suitable for generating microwave oscillations, comprising a central electron emitting cathode, a set of four curved metal plates surrounding said cathode for forming the primary electrons therefrom intdfourmseparate substan-V tially focussed electron beams, a plurality of pairs of metal members surrounding said plates and :forming respective passageways, each passageway having one of its side Walls coated with secondary electron emissive material, and means defining a cavity resonator in communication with each of said passageways.

6. An electron tube of the dynatron type, cornprising, a central primary electron emitting cathode, means dening a plurality of cavity resonators symmetrically located around said cathode, each of said resonators having an individual passageway with one wall of each passageway constituting a secondary electron emitter, and a plurality of electron deecting and focussing electrodes symmetrically surrounding said cathode for causing the primary electrons from the cathode to be formed into a plurality of separate beams one for each of said passageways and for causing each beam to strike only the coated wall thereof.

7. An electron tube according to claim 5, in which the coated side wall of each of said passageways is located at an optimum grazing angle of less than with respect to the said primary electrons impinging thereon to produce maximum secondary emission.

8. An electron tube according to claim 5, in which the last-mentioned means comprises a series of relatively massive metal blocks integral with respective ones of saidside walls to provide 4' heat dissipating means for said side walls.

ERNEST R. JERVIS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,163,157 Samuel June 20, 1939 2,170,219 Seiler Aug. 22, 1939 2,295,396 George Sept. 8, 1942 2,409,038 Hansell Oct. 8, 1946 2,412,772 Hansell Dec. 1'7, 1946 2,416,302 Goodall Feb. 25, 1947 

